Is this the topic under which to discuss Professor Salter’s proposals?
A scientist at the University of Edinburgh has devised a new weapon in the fight against global warming: a fleet of 1,500 unmanned sailing ships creating wakes that whiten clouds to reflect the heat of the Sun better.
I have met Professor Salter, who has a history of being on the right side of the climate argument. He seems thoughtful and rational but when I talk to others who worry about climate change, I am told his proposals are too risky. In the current context should we not take him seriously – we are well past any safe option.
My gut feeling is that his is a route worth investigating. When I saw him a few months ago he was short of funding. Does his scheme deserve the money?
The authors, Drew Shindell in particular, are in the NASA climate modelling group. Shindell is an expert in atmospheric modeling, I gather. He’s written at least one article for realclimate in the past.
This new paper has attracted quite a lot of attention so far. The basic idea seems to be that the strong Arctic warming trend of 1.5 C/decade by comparison with a global trend of 0.2 C/decade indicates that there’s some regional effect which makes the difference from the rest of the planet. The authors single out aerosols, and black carbon, as the likely explanation.
Many of the usual suspects seem to be taking this paper as a sign that NASA has published a report indicating that changes in aerosols are responsible for global warming; rather than greenhouse gases. One report even speculates that Shindell’s position with his boss (James Hansen) has just become more difficult because of this.
[Response: Particularly amusing nonsense, since Jim has been pointing out the importance of black carbon deposition (which replaces the normally highly reflective snow surface with highly absorbing particulates, thus enhancing surface warming) on Arctic warming for a number of years. This effect is additive to the greenhouse gas warming. Any claim by the contrarian noise machine that this (very important) research by Drew and colleagues in any way challenges our understanding of the influence of rising greenhouse gas concentrations on the warming of the Earth's surface suggests a remarkably deep level of confusion, disingenuousness, or both. -mike]
It’s certainly not how I saw the paper. But I’d love to see a clear comment on this from the authors.
[Response: Perhaps we can get Drew to stop by and comment. -mike]
Since the second figure appears hard to read:
The vertical axis shows particle diameter (from 8 to 600 nm),
the horizontal axis shows time (two days in total),
color denotes number concentration, where blue is low, via green and yellow to red (=high).
On Geoengineering, my personal view is that it’s potentially dangerous, but so is unmitigated climate change. Those dangers should be compared, and more research is needed to do so. At this point in time, I would be against active deployment of geoengineering schemes, but in favor of more research into that area.
Duae Quartunciae #2, reminds me of a question that climate experts have told me that the answer is “No”. They are probably right but on these topics it doesn’t hurt to be sure. The question is
Does methane emitted in Arctic regions have any local heating effect before it becomes well-mixed?
I have read that
1. Weather over Siberia can have blocking patterns with little wind.
2. Tamino’s blog, if I remember correctly, mentioned that rises in methane levels can vary by several weeks at different measuring stations.
3. Concentrations of methane near the emitting sources can be hundreds of times greater than background levels. Clearly, if these concentrations reached any height there would be a local warming effect. If these concentrations reached one hundred metres above the emitting sources these concentrations would occupy about one percent of the atmosphere above the source. One hundred times a background level would double the warming effect of methane in the locality.
Warming areas where methane is emitted with methane that is not well-mixed is clearly some sort of feedback. Is it vanishingly small? I would be interested to know if anyone has done the work to dismiss it definitively.
Perhaps it exposes my ignorance to say, but I found it surprising that “[a]lmost all of their properties [...] are size dependent.” Does shape (flat or round) or density play no role in a particle’s tendency to remain airborne? I would think that, what ever effects a particle might have, the need for it to be airborne determines how much of the effect will be produced.
“Many of the usual suspects seem to be taking this paper as a sign that NASA has published a report indicating that changes in aerosols are responsible for global warming; rather than greenhouse gases. One report even speculates that Shindell’s position with his boss (James Hansen) has just become more difficult because of this.”
Ah! Yet another result from denialosphere creative writing machine. I just wonder, are there any constraints on what these guys can write. I mean it seems they are unconstrained by science, history, ethics… Can they construct a lie so bald-faced that even they coundn’t deliver it with a straight face?
Nice post, but how does that compare to aerosol formation during the process of fossil fuel combustion (especially diesel and ship bunker fuel)? Also, how is aerosol formation affected over cities by high level of ozone and peroxyacetyl nitrate (PAN)?
The relative contribution of fossil fuel combustion and biomass combustion to the global black carbon inventory is a matter of some dispute, which is also probably being affected by drought-correlated rise in global wildfires. This can also be seen in the rising rate of tree death across the world:
However, the “global black carbon inventory” is a bit misleading, because aerosols are often the most short-lived component of the atmosphere (which is why regions near dirty coal plants are more soot-blackened than distant regions). This high level of atmospheric variability means that sampling at one or two sites and then project that to the global level is a hopeless exercise – quite unlike the case with CO2, which tends to have a 100-year half-life in the atmosphere. Even with CO2, to avoid the effects of local trends you have to go to places like Mauna Loa and Antarctica to get reliable global-scale measurements. If you like, you can read a discussion of the relative inputs to aerosol clouds here. You could also ask Andrew Revkin to withdraw his still-standing claim that most of the aerosols in atmospheric brown clouds are due to biomass burning.
There are also some important chemical differences in aerosols produced by diesel and ship bunker fuels, especially in combination with ozone, PAN and other air pollutants, for example:
Notice that the effect there is the opposite of the effect of adding volcanic aerosols, which cool the global climate due to stratospheric effects. Removing black carbon aerosols from China and India should have a cooling effect.
The author contends, based on a recent NASA study by Drew Shindell of the NASA Goddard Institute for Space Studies in New York, that reduction of particulate emissions is hurting efforts to reduce global warming from CO2 — an own goal by the Green Team.
The warming at the South Pole (where aerosols are sparse) since the ’70s when scrubbing regulations began is 0.35C, which less than the 1.5C warming at the North Pole (where they are greater). And black carbon absorbs energy (like ozone) and aggravates global warming. However, there is also the global cooling effect of aerosols (such as in nuclear winter). So there seems to be some confusion in public opinion.
Comment by Wilmot McCutchen — 13 Apr 2009 @ 11:51 AM
See the response to #2, Wilmot.
Stop cutting and pasting to “spread the word”. When you do that, it is far too easy to be outed as a non-sentient lifeform.
Having read the response to #2 I respectfully reiterate my wish to point out the confusion in public opinion over the effect of aerosols. Abashed though I am at your rebuke, perhaps my contemptible efforts may serve as a guide to you and other sentient life forms to make a useful contribution.
The statement “… reduction of particulate emissions is hurting efforts to reduce global warming from CO2…” reflects a widespread and fundamental misunderstanding of the role of higher CO2 in forcing global warming. The increased CO2 will behave exactly the same regardless of the levels of aerosols in the atmosphere, changing the energy balance and warming the planet. Aerosols will also change the energy balance, and depending on the characteristics and circumstances, and secondary effects like influence on clouds, can heat or cool the planet.
Saying “reduction of particulate emissions is hurting efforts to reduce global warming from CO2″ is nonsense (or spin from the coal lobby) equivalent to saying “turning off my air conditioner is hurting my efforts to keep my house cool by opening the doors and windows to let in cool breezes.”
I think the Shindell paper (april issue Nature Geosciences) and the attempts to respin it by the fossil fuel lobby together demonstrate how media opinion is far behind the most recent scientific research into climate.
A new study, led by climate scientist Drew Shindell of the NASA Goddard Institute for Space Studies, New York, used a coupled ocean-atmosphere model to investigate how sensitive different regional climates are to changes in levels of carbon dioxide, ozone, and aerosols.
The researchers found that the mid and high latitudes are especially responsive to changes in the level of aerosols. Indeed, the model suggests aerosols likely account for 45 percent or more of the warming that has occurred in the Arctic during the last three decades. The results were published in the April issue of Nature Geoscience.
So, in the scientific world, global warming is an accepted reality, backed up by observations and models – and the questions now are focusing on discrepancies between models and observations. The most obvious one is in the Arctic, where rates of sea ice decline are bypassing the model predictions by a good margin.
This discrepancy is the kind of thing that brings scientific attention – that’s how the model/observation approach works – it’s when the model fails that you learn something new. That’s the reason why the paper was considered significant.
So, if we make up a list of possible reasons for the model’s failure to predict Arctic intensification, we can include:
1) aerosol effects
2) dynamic increases in poleward heat transport
3) sensitivity of thin sea ice to wind forcing
The Shindell & Faluvegi paper seems to indicate that aerosols are the largest unaccounted factor in the climate models. Their abstract begins:
Regional climate change can arise from three different effects: regional changes to the amount of radiative heating that reaches the Earth’s surface, an inhomogeneous response to globally uniform changes in radiative heating and variability without a specific forcing.
Those three correlate with the three factors I listed, sort of. There may also be additive effects, i.e. natural variability imposed on polewards heat transfer and sea ice (the Artic Oscillation, say).
In any case, it is simply an effort to reconcile the rapid rates of warming in the Arctic with the output of the most recent group of global climate models – everyone agrees that global warming is real, except for a very large number of editors and reporters with the U.S. press, who continue to advocate for the positions held by a small number of fossil fuel funded contrarians and insist on giving them “equal time” – a luxury denied to renewable energy experts. In the area of climate, scientists and denialists get equal time – but in the area of energy, the only side that you hear from is the fossil fuel lobby and their front groups.
The denialist intentional confusion between CO2 and aerosols is an example of why ALL college students, regardless of major, should be required to take the “Engineering and Science Core Curriculum.” Even drama, music and English majors should be required to take Engineering and Science Core Curriculum so that those who wind up doing a lot of writing will have some contact with reality. As it is now, they see everything as a word game. They need to be shown that NATURE is the boss, not the person with the fanciest rhetoric.
I just asked my 9 and 11 year old sons whether the natural world controls our environment or someone who tells a good story. Both were quite capable of selecting mother nature as the boss. I doubt it is necessary to dictate course selections to college students.
“Our reconstructions broadly agree with historical emissions estimates, and can explain the differences between observed changes in Arctic temperatures and expectations from non-aerosol forcings plus unforced variability.”
So observations are a bit more in line with expectations.
Off-topic a bit…Hargreaves & Annan have recently published a comment on a study by Chylek & Lohmann, which suggested lower climate sensitivity. The authors show that Chylek & Lohmann selectively used a few unrepresentative outlier data points to gain the lower estimate. They show that by selecting unrepresentative data and using the same methodology, they can also estimate higher levels of climate sensitivity than the 3 C IPCC best estimate.
Geoff Beacon (1) — I recommend a e-mail to John Holdren at the White House.
Comment by David B. Benson — 13 Apr 2009 @ 4:08 PM
Re The response on comment #2 by Mike:
“…. the importance of black carbon deposition (which replaces the normally highly reflective snow surface with highly absorbing particulates, thus enhancing surface warming) on Arctic warming for a number of years. This effect is additive to the greenhouse gas warming.”
This is pretty straightforward, and easy to understand by non atmospheric scientists,like myself. The albedo or reflectivity of the ice surface is decreased by coating the surface with black particulates which don’t reflect but absorb the heat from the Sun.
No rocket science here(though this a misnomer). Anyone who reads more than this into the subject is probably up to some kind of mischief.
“just asked my 9 and 11 year old sons whether the natural world controls our environment or someone who tells a good story. Both were quite capable of selecting mother nature as the boss. I doubt it is necessary to dictate course selections to college students.”
Aerosols _are_ part of the natural world. It’s just they have been moved from one place or state to a different one.
CO2 is part of the natural world, as above.
Everything is part of the natural world.
I find the article on aerosols informative and understandable by not-too-scientific minds like myself. I have book marked it
“Does shape (flat or round) or density play no role in a particle’s tendency to remain airborne?” Yes, but their effect is minor compared to that of particle diameter.
The effect of particle shape is sometimes included by multiplying the size by a ‘shape factor’ to arrive at an “effective diameter”: the diameter the particle behaves as. For atmospheric aerosol, this shape factor is usually not strongly different from one; its effect is usually assumed negligible compared to the effect of particle size, which covers several orders of magnitude. An exception is e.g freshly emitted soot, which is far from spherical (see some pictures of archetypical aerosol types here; soot = Russpartikel). Upon chemical transformation in the atmosphere, most aerosols become more or less spherical.
As for particle density, that also has a limited range (factor of two), so its effect is also very minor compared to that of particle size. Besides, everything depends on size, but not everything depends on density. Settling by gravitation depends on mass and thus on density, but that’s a relatively minor loss process at least for submicron aerosol. And in that case the diameter is having its effect raised to the cubed power.
Ike Solem (8):
I don’t know the specifics, but eg in the exhaust stream of cars the high supersaturation of organic compounds causes continuous nucleation, and indeed the exhaust pipes emit a lot of freshly nucleated nanoparticles of typically around 10-20 nanometers in diameter. In powerplant plumes or shiptracks nucleation can occur because of elevated levels of SO2 (which forms H2SO4 after photo-oxidation). High ozone levels downstream of pollution sources can cause elevated OH radical concentrations, which in turn increases the concentration of condensable species and thus the potential for nucleation. But the aerosol surface area is usually larger as well, and that would suppress nucleation. It’s not immediately obvious which process would win, but its effect would be extremely hard to detect regardless.
Good point about the difference in variability between aerosol and GHG.
From a climate perspective, it’s much better to leave your car standing and ride a bike than paint your roof white.
The suggestion of spraying sea salt particles into the air is an example of adding primary aerosol particles to the atmosphere. This is different from nucleation, which generates new /secondary/ aerosols via gas-to-particle conversion.
The idea behind spraying sea salt into the atmosphere is to increase the concentration of cloud condensation nuclei (CCN), which should increase cloud brightness (albedo) via the Twomey effect (and possibly increase cloud lifetime).
Of course the effect of black carbon is additive. The effect would be to increase the Arctic temperature from what would have been caused by greenhouse gasses by themselves. This has the opposite effect of “white” aerosols which were damping the temperature increase.
[Response: Yes, that's the point. Thanks for restating it. This seemingly obvious point is apparently lost on those who argue its an "either/or" proposition (i.e. the fatuous implication that somehow the research in question suggests that greenhouse gases are not primarily responsible for the observed warming of the globe). -mike]
To what extent do you believe black carbon has increased the measured Arctic and global temperature trends?
[Response: Firstly, its not a matter of "belief", let alone what I believe. There is a solid literature on all of this, and there are entire chapters on this in the IPCC reports. The bottom line is that reflecting aerosols, at least, thusfar, have dominated the global mean anthropogenic aerosol forcing. That means that anthropogenic aerosols have been a mitigating factor when it comes to the warming of the globe over the past century. There is nothing in this latest study that challenges that. For the Arctic, its an entirely different story. Black carbon has likely played a far more significant role there, because of the contrast between absorbing aerosols deposited on the ice surface, and the high albedo perennial ice cover, and thus in this particular region black carbon has likely been an aggravating factor when it comes to anthropogenic surface warming. I apologize for leaving all of this implicit in my brief, original comments. For further details, see the IPCC AR4 Working Group I report (see in particular sections 2.4 and 2.5 of chapter 2). -mike]
Comment by Nicolas Nierenberg — 13 Apr 2009 @ 5:58 PM
Thank you for providing this very well written and easy to understand synopsis Bart. Very helpful, especially for ignoramuses such as myself.
Imagine a 50 million dollar way to manufacture enough cooling clouds to offset AGW for as long as it takes to get emissions under control.
I’d say, even if that idea has only 10% merit today, it’s well worth taking seriously and exploring.
These are some of the concepts we are going to need to explore as we go forward. I’ve seen one or two of you stating as a given that emissions reduction will not be enough.
But I have no intention of hijacking three posts in a row, and I will decline to pursue that thought any further in this thread.
Let me just say the idea expresses a strong sense of rationality (working with nature the way nature works) and realism (we’re going to need to do more than we’re doing). On that basis alone it deserves notice.
would like to know how much aerosols were produced during WW2, the Korean and Vietnam Wars? If one looks at the global temperature variations during these periods one observes a declining temperature trend. Could there be a cause and effect relationship? I have been alife during that time and observed the enormous dstruction during these wars. For ore details review the monograph of Enrico Fabrizius \A Painful Reality\. Thanks for responding. Heinrich Schmid.
Comment by Heinrich Schmid — 13 Apr 2009 @ 11:05 PM
> William @18: Well, what can we say about someone who gets his science advice
> from 9 and 11 year olds.
More to the point, those kids tend to have their curiosity intact. Something many manage to lose as they “grow up”. Is it too far out to suspect, like Edward Greisch does, that the education system has something to do with that?
Comment by Martin Vermeer — 14 Apr 2009 @ 12:03 AM
Very well written article Bart, thanks for the effort. James Dorsey much appreciates the links to the introduction to his first year report from his Ph.D. Look forward to part 2.
I had this tome foisted on me. I’d put this in the mostly natural category. To discuss.
“Melankovitch cycles also influence warming, not just cooling, and we are in a warming period of the cycles. As I believe I said earlier, but of course why let little things like that stand in the way of your continual pseudo-intellectual efforts to build your ego up. But, I guess, what can one expect from someone of the bent who judges scientific research on the basis of one’s own perceived political interpretations and labels it all knowing or conservative denying in turn.
But if we want to talk about things that man does impact greatly, CO2 releases would be one of them. However, the assumption invariably exhibited that industrial releases by us is the greatest cause of this is so incorrect it is laughable. The simple act of some civilizations trying to feed and clothe their members through subsistence existences is by far a larger source to the extent that the United States could stop all emissions this very second along with the industrialized world and CO2 levels would still be projected to increase by a factor of 3 by 2100. Deforestation from subsistence groups, primarily in Africa and South America, produces 30% of the total global CO2 release while industrial sources contribute 14%.”
[Response: Very wrong. Last figures available show about 7 GtC/yr from industrial (fossil fuel/cement) and ~2 GtC from deforestation. - gavin]
“I’d put this in the mostly natural category.” – Mark A. York
I’d say the rubbish you received also has a large component of “blame it on the poor” (a.k.a. “blame it on the dark-skinned”). The writer’s use of “industrial sources” as a comparator with deforestation is either ignorant or disingenuous: most of the industrialised world’s CO2 production is from domestic use, travel, land use change and other “non-industrial” activities. Moreover, a large proportion of deforestation is not taking place for subsistence agriculture, but for cattle ranching, oil palm plantations, timber extraction and other commercial enterprises – many of which are supplying raw materials to the rich world.
“Aerosols are liquid or solid particles suspended in the atmosphere (but not including water droplets or ice crystals)”
I think this is likely to be misinterpreted. By mass aren’t most aerosols in the atmosphere mostly water? While water may not be significant in the formation of the aerosols it can play a big role in the growth and evolution of particles.
The first link in the first post mentions that some accumulate water, and so wash out as rain.
Poking around with Scholar, I found mention of “hydrophobic soot particles from residential coal and industrial oil burning” and also mention of radar being used that distinguishes aerosols from water vapor and clouds.
Re #37: “Melankovitch cycles also influence warming, not just cooling, and we are in a warming period of the cycles.”
Noone has yet commented on this sentence from the person who you are corresponding with, so I’ll take a crack.
First of all, I wonder where he is getting the idea that we are in a warming period of the cycles. The long term trend is actually expected to be toward cooling, being that we are in an interglacial period. I guess it was originally expected that “long term” meant over say the next 20,000 years (as Shackleton et al talked about in their classic 1976 paper in Science)…although some of the latest work predicts this interglacial period would (even in the absence of human interference) be expected to last longer, as I recall perhaps another 50,000 years. Now, it may be that along with this longer interglacial comes the idea that over shorter timescales (of, say, 10000 or 20000 years) we would actually expect some a little warming although I haven’t heard this case made…and would expect that any such effect would be quite modest.
Second of all, Milankovitch cycles operate on much longer timescales than the timescale of a century or so that are of interest to us at the moment. Even the warmings out of the glacial periods into the interglacials only occurred at an average rate of something like 0.1 C per century (with coolings generally being even slower). So, even if your correspondent were correct in his claims about where we are in the cycles, I don’t think it could account for very much of the warming.
Water droplets and ice crystals are usually treated separately from aerosols because of their different nature. However, the distinction is not always crystal-clear.
Most regular aerosol particles contain water, the amount of which depends on the hygroscopicity (=water affinity) of the aerosol and on the relative humidity (RH). At 95% RH, water is perhaps the dominant compound in most aerosol types, but at say 50% RH, that’s not the case. The phenomenon of haze limiting visibiliy is often aggravated by a high RH, causing the aerosols to grow in size as a result of picking up more water. Since they’re bigger, they scatter radiation more effectively, hence the aggravating effect on visibility.
Freshly emitted soot is an example of a hydrophobic aerosol type; after chemical transformation in the atmosphere (e.g. oxidation of its surface rendering it more hygroscopic; condensation of more hydrophilic species onto the particle) it will gradually pick up water as well.
Radar distinguishes cloud droplets (~10 micrometer) from aerosol particles (number dominated by those
Since it’s been known for some time that black carbon is a significant cause of Arctic warming, what is the reason that it and other aerosols have not been factored into the climate models —for what reason would such an important factor be left out?
It seems especially important in the light of the research and findings by Lehmann et al on black carbon in soils—- its very slow decomposition rate—–and the fact that climate models may be over-estimating their global warming predictions, if they are not including ‘realistic stocks of black carbon in prediction models’.
Re: Truth (#45): Speaking of the Lehmann et al. study, I thought that it might be nice to have realclimate do a response to it. I did send a note to the Cornell press office along these lines:
“I read the recent report of Professor Lehman’s study on black carbon in Australian soils with interest. However, I might suggest that the implications of the study for global climate projections have been overstated. The positive feedback of increased soil temperature leading to increased decomposition and therefore natural carbon emissions is a fairly modest contributor to the total projected business as usual carbon emissions over the century: average IPCC AR4 model land carbon storage changes due to climate change yielded a 63 ppm CO2 increase over the counterfactual by the year 2100. Therefore, an assumption that the 20% reduction in land carbon storage resulting from the Lehman et al. work holds globally would yield a reduction on the order of 13 ppm. 13 ppm, while not negligible, and certainly of significant scientific interest, is still small in comparison to the several hundred ppm increase expected in the business as usual case.
Therefore, I would suggest that the title of the Cornell news release “Global warming predictions are overestimated, suggests study on black carbon”, while technically correct, is rather misleading in that a casual reading would infer an “overestimate” rather larger than the couple percent implied by the study.And, indeed, the news release in being cited in a number of places on the internet as evidence climate change fears are being overstated.
If I misread the study I apologize, but I do believe that a rewording of the news release would reduce the potential for misinterpretation, and I thank you for your attention,”
I got a polite, agreeable, but somewhat non-committal response to my comment from Prof. Lehmann. Truth, you might also want to note that “soil black carbon” is a completely different beast from the aerosol black carbon issue.
Here, from the lead paragraph of the most recent post, is all you need to know about the source from which “truth” obtains his (her, their?) ‘truths’:
New Scientist, also known as Nude Socia.list [spam block avoider there] magazine, never misses the opportunity to use the derogatory phrase ‘climate-change deniers’ in order to smear sound scientific argument against an unverifiable computer modelled catastrophe driven by harmless aerial plant food gas.
‘Nude Socia.list’, oh man that is too funny? I spit coffee all over the desk when I read that. Actually all kinds of funny stuff over there. That guy must write for Letterman.
Jim, that’s a veritable workshop on how to pack the most loaded modifiers into one sentence–albeit at the cost of redundancy and vagueness. (If there’s “aerial plant food gas” can there be “terrestrial plant food gas?” And does aerial modify “plant” or “gas?” EB White would not approve.)
(Captcha disapproves, too: “final-exam rented” and then “copying securely”)
“Since it’s been known for some time that black carbon is a significant cause of Arctic warming, what is the reason that it and other aerosols have not been factored into the climate models —for what reason would such an important factor be left out?”
It’s ok, you can come out and say what you’re thinking… It’s a conspiracy! For a pittance of free conference travel, the possibility of an upgraded office with south-facing windows plus a few other perks the entire scientific community (apparently starting as far back as the mid-19th century) has constructed a nefarious and intricate plot, caring not a whit about their drastic and unfair impact on everybody else! Horrific, but then life is hardly fair– just ask ExxonMobil’s board of directors about the suffering they’ve been incurring at the hands of the malefactors.
My suggestion is that you resign as footsoldier for the beleaguered, temporarily and only coincidentally rich-as-Croesus industrial victims you’re so bravely defending, join the conspiracy, get in on the free coach class and peanuts. If you can’t bring yourself to sign on for all the largesse you’ll receive (free Internet with classy “.edu” TLD, etc.), watch out for scientists with white Persian cats, dueling scars and weird middle European accents; ff you can turn around fast enough you just might see them huddling together as they perform the difficult task of falsifying diverse observations from disparate fields in a way that consistently supports their conspiracy (an effort some might say is not worth it compared to earning billions as an industrialist, but the human nature is –so– complicated).
Marcus and twuth, the discussion of the Cornell study on soil carbon has little to do with aerosol topics, and everything to do with the response of the carbon cycle to warming temperatures – something that climate models do not attempt to take into account. Instead, climate models using CO2 forcing scenarios chosen by researchers – educated guesses about future human behavior and carbon cycle responses. (These are the IPCC scenarios).
Soil carbon trends are due to a balance between photosynthesis, respiration, and burial. A leaf falls to the floor, and is largely digested back to CO2 by fungi and microorganisms – but some fraction ends up residing in soil for thousands of years before finally making its way back to the atmosphere.
What the Cornell study shows is that in Australia, much of the soil carbon is built up due to wildfire activity, rather than microbial activity. This kind of charcoal-based soil carbon is remarkably stable relative to leaf-fungal humus, and as the planet continues to warm, such soils should be fairly stable and there should be little positive feedback effect.
This area of science is called “biogeochemical modeling”, and involves more than just carbon. For example, there is a nitrogen cycle that continually interacts with the carbon cycle, and often determines the rate of the carbon cycle – along with temperature and many other variables.
It is a good example of how denialists are trying to distort scientific research, however. Here is the original news release on the Cornell Paper:
As a result of global warming, soils are expected to release more carbon dioxide, the major greenhouse gas, into the atmosphere, which, in turn, creates more warming. Climate models try to incorporate these increases of carbon dioxide from soils as the planet warms, but results vary greatly when realistic estimates of black carbon in soils are included in the predictions, the study found.
The story was then picked up by the physorg.com website, which respun it:
The paper says nothing about the ability of modern climate models to produce realistic predictions, despite what that headline implies. The site put on a new title, removed the first two sentences, and stuck in a new header:
(PhysOrg.com) — A detailed analysis of black carbon — the residue of burned organic matter — in computer climate models suggests that those models may be overestimating global warming predictions.
Again, those would be climate models that attempt to do biogeochemical predictions – a whole new subject, with the largest uncertainty being future human behavior – and there are no reliable equations for that one. They are not talking about how modern climate models treat aerosol forcing.
Just a tad bit misleading, isn’t it? Physorg.com is owned by a technology consulting company, Omicron Technology Ltd. “We get people talking”, is part of their advertising line.
We now get back to the link cited by “truth”, which directs readers to physorg.com:
That link points us to the misleading and re-spun physorg.com version, not the Cornell press release. It also includes the following dishonest claim:
“The findings are significant because soils are by far the world’s largest source of carbon dioxide, producing 10 times more carbon dioxide each year than all the carbon dioxide emissions from human activities combined. Small changes in how carbon emissions from soils are estimated, therefore, can have a large impact.”
In fact, the biosphere is thought to exchange as much as 100 gigatons of carbon in either direction each year – photosynthesis and respiration – compared to the 6 gigatons of fossil fuel CO2 added each year. The key difference is that the 6 gigatons of carbon is fossil carbon – it is not part of the normal carbon cycle, but rather lifts the level of all pools – more CO2 in the atmosphere and in the oceans.
Thus, one could say that plants and soils are also the biggest sink of carbon dioxide on the planet, as they absorb at least ten times as much CO2 each year as is emitted by all human activity. Thus, there is no problem – all the CO2 is sucked up… or is it?
The soil absorbs and emits vast amounts of CO2 each year, but is in steady state overall – a thousand years ago, the situation was much the same as it was a hundred years ago. The argument being made is similar to one claiming that evaporation isn’t balanced by precipitation, so the oceans will eventually evaporate away. X billion tons evaporate every year, so if you divide ocean mass by X you see that they will soon be gone…
The actual paper is part of the very active scientific effort to understand potential feedbacks in the carbon cycle – soil carbon is a big one, as is permafrost, and possible ocean circulation changes. It in no way alters current scientific consensus on climate model reliability.
Practically, what the paper says is that biochar amendments to soil are very stable – and so far, biochar is the only realistic carbon sequestration and storage program out there.
> MikeB, 13 April 2009 2:35 PM, Shindell 2007 NYT, Nicolas, TAR ….
Could y’all _please_ move a conversation about tha telsewhere? This is
“Aerosol formation and climate, Part I” –we have a reading list at the top, we have the scientist here to teach, for now. Digress-> egress?
“be Clonin” says ReCaptcha. Like, copy yours somewhere else.
Trying myself; Ike brought up the new Shindell paper. Okay, yeah, it agrees aerosols are the big uncertainty. But the topic is about what the factors are.
Dr. Verheggen, you gave us a great many factors in the first post that affect what becomes an aerosol, how long the stuff stays in the air, how fast it grows from its original size (if it does), how big it has to get to change how it behaves.
The first three links are to the introductory stuff. I’m trying.
Gee, climatology is hard ….. (third paper is German language — anyone able to translate? Anything unique there that’s not in the first two introductory papers?)
Then you pointed to the discussion of uncertainty, with the link to the PDF copy of Atmos. Chem. Phys., 5, 715–737, 2005
Global indirect aerosol effects: a review; U. Lohmann, J. Feichter.
(Ike, did you compare Shindell to that paper, for Nicolas’s question?)
I’m just starting to try to read this.
You know, this reminds me of hearing performance majors talk about learning music at college — how for the first few years they could no longer just enjoy music, because they were starting to learn to notice elements and how they fit together and changed over time, and it was as though the music was falling apart (this was before pixels …).
I realize you’ve given us basic introductory reading here — and it’s dense, complicated, new, and amazing. And it is making just looking at the blue sky a little difficult right now. It’s full of stuff!
Dr. V. — of the factors you listed, or the introductory papers you gave us listed — do you have grad students building the instruments to detect this kind of thing? Are you using off the shelf gear? Is there anything you “know is there but can’t measure” in the air? And are you working with any of the sediment/coring people to figure out how what’s in the air becomes whatever they find in mud or ice cores?
I imagine as you’ve showed us it changes for weeks while floating around, that it continues to change after it falls into ice and freezes, or salt or fresh ice or water, and eventually sinks and ends up in mud layers.
Does anyone do experimental work putting material into air (maybe in a big Zeppelin hangar or something?) and waiting a few weeks without any air movement and looking at the layers that fall out, say?
Do you have any good radioactive tracers, say from the surface bomb tests, that help identify ‘airborne’ aerosols with whatever they become by the time a stratigrapher finds them in the mud or ice?
Heinrich Schmid (33),
I’m not aware of any estimates to what extent these mid-century wars contributed to climate changes, but I suspect it’s less than you’d estimate from the enormous destruction. Aerosol emissions from industrial sources are likely to be dominant in terms of climate.
Hank Roberts (56),
The prime thing relevant here that we “know is there but can’t measure” are the conglomerates of molecules leading up to a stable aerosol particle. Both their number concentration as a function of size, and their chemical composition (which is only being measured from a much larger size, say 20 nm). There are interesting developments in this area though, eg the AIS (air ion spectrometer), measuring the number size distribution of charged ions and clusters between 0.5 and 40 nm. I’m not working on instrument development myself, although that is an active area of R&D in the group I work at. As yet, we don’t collaborate with ice core/sediment researchers. An active area of research is based on simulating atmospheric reactions in so-called smog chambers. Waiting a few weeks is hardly possible tough, since most particles will have been lost to the walls of the chamber by then. It’s only recently that groups started to look at longer timescales of eg 60 hours, to look at chemical transformations that occur over those timescales, relevant for atmospheric aging processes.
#53: Ike Solem: Fascinating! I am 99% sure that at the time I wrote my email (Nov 20th) the title of the Cornell news release was in fact “Global warming predictions are overestimated, suggests study on black carbon”: in fact, if you look at websites that picked the story up they cite the original title.
Therefore, the author must have changed the title at some point after I wrote my email. It is nice to see that press offices do fix things when alerted to possible miscommunications (not saying that it was due to my email alone – I wouldn’t be surprised if other people wrote to them too).
Note to Marcus: No, the author did not change the title or had the deceptive header – that was done by the editors of the web sites who picked up the story and respun it. Journalists don’t get to pick headlines – that’s the editor’s perogative – or that of the public relations agency, I suppose. For a recent example of how this works, see this story on Hill&Knowlton and Burson-Marstellar.
Hank, you say:
“Trying myself; Ike brought up the new Shindell paper. Okay, yeah, it agrees aerosols are the big uncertainty.”
Hmmm… “Duae Quartunciae” brought up the topic, I thought. The Shindell paper reduces the uncertainty regarding the aerosol effect in the Arctic, and helps close gaps between models and observations. It’s not the only plausible explanation of the observed trends, but so far seems the most likely.
However, it is worthwhile to compare and contrast the Shindell & Faluvegi paper with another recent aerosol paper:
Here, we elucidate this question by using 26 years of satellite data to drive a simple physical model for estimating the temperature response of the ocean mixed layer to changes in aerosol loadings…
Which is more reliable, and why? Are their conclusions similar, or mutually exclusive? Notice that Evan et al are saying that aerosol changes over the tropical Atlantic have a warming, not a cooling influence… Apparently, the only factor in the warming oceans in the Atlantic is a reduction in dust from Africa over the past ? years…
To better determine the extent to which aerosols have contributed to the evolution of this tropical North Atlantic temperature anomaly, we subtract our monthly estimates of the oceanic cooling by dust and stratospheric aerosols from the observed tropical North Atlantic SST and plot the anomaly of the residual (Fig. 3). This is our estimation of variability in northern tropical Atlantic SST that is not directly driven by local changes in aerosols, which we will refer to as the residual SST. The trend in the residual SST time series is 0.08°C/decade (Table 1 and Fig. 3), 0.17°C/decade weaker than the trend in observed SST (Fig. 2B) and not statistically significant (23). These calculations suggest that 69% of the recent upward trend in northern tropical Atlantic SST is due to changes in aerosols
There is a rather obvious ongoing effort to blame global warming on aerosols, as seen in Australia:
“The Sahelian drought may be due to a combination of natural variability and atmospheric aerosol. Cleaner air in the future will mean greater rainfall in this region,” Leon Rotstayn, an Australian government researcher, said in a recent report – Washington Times, 2002
CSIRO has a long record of supporting coal industry propaganda:
The Shindell paper seems far more reliable than the Evans paper, overall – and the reason is that they use a complete global coupled model, not a “simple physical model”. The Evans et al. “estimate of the direct effect of dust radiative forcing on the upper-ocean heat budget” doesn’t seem very reliable for that reason alone. Their simplistic treatment of aerosols also doesn’t help much (they assume two types only with very specific optical properties (“sulfuric acid” and “dust”), and zero black carbon).
It’s pretty surprising that a paper that used such simplistic approaches was selected for ScienceExpress publication, isn’t it?
As far as uncertainties, the big one is not aerosols, but future human behavior. That will be the single largest factor in future climate outcomes.
Ike: My recollection was that at the time, that was the title used on the Cornell website, as well as by all the sites that picket it up. I don’t know that I have any evidence of that, not having taken a screenshot at the time, but like I said, I’m 99% sure that the “deceptive” title was the original title at the time I wrote my email (November 20th). And therefore, I am presuming that the Cornell news office has changed the title, but all the sites that link to it are still using the original title.
There definitely seems to be a campaign in the media to use any aerosol research as “proof” that CO2 is not the principal cause of AGW. The Shindell paper was reported at The Register with the headline: “NASA: Clean-air regs, not CO2, are melting the ice cap”.
I tried posting a comment asking for the headline to be changed, but it got nixed, and I also complained to the editor, but got no response. It might be an idea for Shindell or someone else at Goddard to drop a line to The Register asking them to correct their inaccuracies.
Today’s New York Times has a front page article by Elisabeth Rosenthal about the effects of Soot from third world stoves on AGW.
It reads in part:”While carbon dioxide may be the No. 1 contributor to rising global temperatures, scientists say, black carbon has emerged as an important No. 2, with recent studies estimating that it is responsible for 18 percent of the planet’s warming, compared with 40 percent for carbon dioxide. Decreasing black carbon emissions would be a relatively cheap way to significantly rein in global warming — especially in the short term, climate experts say. ” http://www.nytimes.com/2009/04/16/science/earth/16degrees.html?_r=1&ref=todayspaper
Jim Bouldin and Doug Rostram:  
You really have lost it completely, haven’t you.
The implication from your attack seems to be that the only people in the world who are above questioning are the scientists and the true believers of AGW—that any other citizen of this world who just raises findings [ by other credible scientists] that you see as a threat to the firewall, —-must be verbally annihilated —it’s pathetic.
I am just an Australian who wants the correct decisions made on the best possible evidence, for the sake of my children.
You say the models don’t attempt to take into account the feedback response—
‘the response of the carbon cycle to warming temperatures – something that climate models do not attempt to take into account.’
But later , you cite the Cornell paper —
‘Climate models try to incorporate these increases of carbon dioxide from soils as the planet warms, but results vary greatly when realistic estimates of black carbon in soils are included in the predictions, the study found.’
You blame Phys.org for the ‘over-estimating climate predictions ’ quote—–but the actual press release from Cornell begins with the following statement:
‘A detailed analysis of black carbon – the residue of burned organic matter – in computer climate models suggests that those models may be overestimating climate change predictions.’
The statement from Phys.org, that you call dishonest , also comes straight from the Cornell press release, below:
‘The findings are significant because soils are by far the world’s largest source of carbon dioxide, producing 10 times more carbon dioxide each year than all the carbon dioxide emissions from human activities combined. Small changes in how carbon emissions from soils are estimated, therefore, can have a large impact.’
In your attack on the CSIRO, and on Evans et al , in [ 59], you appear to be saying that any researchers who do any research, or come up with any findings that suggest new factors,or that soften the alarmist rhetoric , or seek to find ways to use coal more cleanly, are just purveyors of blame and ‘propaganda’.
The CSIRO, that you accuse of being a propagandist for the coal industry, is firmly on your side of this issue—but the crime in your view seems to be that they would have the temerity to seek to find ways to cut the CO2 emissions from coal-burning , or eliminate them—which is the subject of the two links you provided.
How realistic is that attitude, when China is still commissioning coal-fired power stations on a weekly basis—Obama is now agreeing that coal will be with us for decades—and Germany [ even or especially its Greens party] is planning at least 12 new coal-fired power stations?
Interesting, Lawrence – the NYT persists in insisting that black carbon is from wood stoves, and has nothing to do with ship emissions or diesel truck emissions or perhaps more frequent wildfires.
In Asia and Africa, cookstoves produce the bulk of black carbon, although it also emanates from diesel engines and coal plants there. In the United States and Europe, black carbon emissions have already been reduced significantly by filters and scrubbers.
In reality, studies show about a 50-50 split between fossil and biomass sources of black carbon, although data collection is quite poor. For biomass burning to be the culprit, there must have been quite the explosion in biomass use recently as compared to past eras. India’s population has roughly doubled in the past half-century, but it’s not clear that this would double biomass-sourced black carbon emissions. On the other hand, records show that India has increased fossil fuel use by a factor of at least 10, possibly 20, in the past half-century. And yet, we are informed by the NYT that the culprit is poor people burning dung.
It certainly plays a role in the total black carbon aerosol load over India and the Indian Ocean – but fossil fuels are responsible for the vast majority of the addition – just look at the numbers.
The other thing is that black carbon emissions from diesel trucks and shipping in the United States have not been reduced (much) or eliminated, as the NYT claims:
I’m not sure why the NYT is so insistent on ignoring shipping and blaming poor people for the atmospheric aerosol clouds, other than that it fits standard practice for diehard boosters of the “uncontested benefits of global trade”. Resource extraction is not responsible for environmental destruction, we learn, poor people are. What is particularly nauseating is how they try and use Ramanathan’s quote to push the PR agenda – ask yourself why they didn’t instead use the lead sentence from Ramanathan’s 2005 paper:
South Asian emissions of fossil fuel SO2 and black carbon increased 6-fold since 1930, resulting in large atmospheric concentrations of black carbon and other aerosols.
I agree,Ike, that the Times article could have ( and should have) put more emphasis on other sources of black carbon. Though I don’t believe that the Times has any bias against the poor. They don’t rely on the shipping industry to remain solvent.
I’m not too familiar with this writer’s work,but Andy Revkin, who also covers global warming and related topics for the Times has had an objective approach.
In any case Dr. Ramanathan considers the reduction of black carbon from this source to be serious enough that he returned to his homeland to deal with the problem.
Comment by Lawrence Brown — 17 Apr 2009 @ 12:49 PM
“More recently, Ramanathan showed that South Asian “brown clouds” caused by the burning of fossil fuels could lower ocean temperatures, slowing down monsoon circulation and reducing seasonal rainfall. In a pioneering study with agricultural economists, he linked the phenomenon to a significant decrease in the Indian rice harvest. He has also linked the combined heating effect of greenhouse gases and brown clouds, which contain soot, trace metals and other particles, to the recent retreat of Himalayan glaciers that supply drinking water to billions of people.”
In particular, he’s known for the use of UAVs to sample atmospheric clouds, which was done in Beijing recently.
It’s true that providing clean energy for cooking is necessary for India’s rural poor, but so is the replacement of diesel-powered transport with solar-powered transport.
I must admit I do not find Andrew Revkins reporting to be very objective as of late. Compare the above Tyler prize report with Revkin’s blog on the topic:
“The smoke is rising mainly from cooking fires fueled with firewood or dried dung.”
That looks like respinning the press release to change the emphasis from fossil fuels to wood and dung fires, not like objectivity.
Now, for the truest of the true:
1) There are weather models which use sea surface temperatures and other climate variables as input for one-week forecasts
2) There are climate models based on weather models, and they are driven by external forcings: greenhouse gases, for example
3) There are biogeochemical models which attempt to estimate the rates of carbon cycling, nitrogen cycling, sulfur cycling, and so on. This is the kind of model that the paper addresses.
Our current estimates of climate sensitivity are based on climate models that use CO2 emission profiles which are set by researchers.
By far, the largest uncertainty in carbon cycle modeling is future human behavior.
Another uncertainty is what will happen to carbon stored in permafrost and in soils as the temperatures warm – will much of it be converted to CO2, or not? The paper in question shows that biochar is a very stable form of carbon, unlikely to be converted back to CO2 as the climate warms. Thus, biochar is the leading candidate for effective carbon burial over geological time periods – which is the only way to reduce atmospheric CO2 concentrations (assuming you’ve already replaced fossil fuel combustion).
Clearly, the web sites in question distorted the meaning of the original article in a transparent attempt to cast doubt on climate model conclusions – although it is true that the original author could have been a little more clear about what kind of models were being discussed.
In his white paper on the subject of elemental carbon Ramanathan says:
“Biomass burning and biofuel cooking are the major sources of EC emissions in India and other developing nations. The current international emphasis in global warming mitigation is on carbon dioxide, whereas the main focus of Surya is on EC, for reasons given in the next few sections.” http://www-ramanathan.ucsd.edu/Project%20Surya/Surya-WhitePaper.pdf
The paper goes on to say:
“……..75% of households in India, use biofuels and biomass, including wood, charcoal, crop residues and dung, to prepare food and heat their homes.9 More than 70% of India’s population lives in rural areas. Cooking accounts for about 60% of the overall energy and 80% of the non-commercial energy used in rural India. More than 90% of the cooking is done with fire wood and bovine dung, i.e, cow-dung10″
“Soot and other particles in ABCs lead to a large reduction of sunlight at the ground and, in addition, lead to large atmospheric solar heating.”
It appears that Revkin is correct in saying that the smoke and soot are mainly from cooking stoves in this area.
Comment by Lawrence Brown — 18 Apr 2009 @ 11:14 AM
How much warming from GHG’s is being offset by the cooling effects of aerosols? Less than one degree? More? How much more or less?
Another question I have is when gavin (I think it was) says that industry emits 7GtC/yr does he mean CO2, CO2 equivalent, or actual carbon? If the latter, what is the conversion factor to get annual tonnage for CO2? Does this ignore non-CO2 sources of GHG’s with carbon like methane?
Thanks ahead of time for any light anyone sheds on my dimness.
Wili (68) — Since it is carbon inthe active carbon cycle which matters, these emissons figures are typically stated in terms of C. But it is, of course, mostly CO2; 7 GtC = (44/12)X7 = 25.7 GtCO2. Methane contributions of carbon are rather small, but I haven’t the figures. Try the Carbon Dioxide Information Analysis Center at ORNL for more.
Comment by David B. Benson — 19 Apr 2009 @ 6:34 PM
Wili (68), 7Gt/yr would be only the carbon in the CO2.
The molecular weight of carbon is 12, that of the O2 is 16×2, so CO2 is 44. Multiply the carbon weight by 44/12 to get to the weight of CO2.
Re#68 by Wili: This is in partial answer to your questions
“Based on records of activity in the energy and transportation sectors of the economy and on correlations with
economic growth about 7 GtC (carbon) per year were injected into the atmosphere from 1995 to 2005 . Additionally,roughly 1 GtC/yr was injected” from forest burning.(the quoted part is from “Climate Change-Picturing the Science”by Gavin Schmidt and Joshua Wolf, page 146)
This represents actual gigatons of carbon. To get the the tonnage for CO2 multiply the carbon tonnage by 44/12 or ~3.67. This is because carbon has an atomic weight of 12 and oxygen has an atomic weight of 16.Then the weight of a CO2 molecule is 12 + 2×16=44.
Ergo the weight of C02 released into the atmosphere by burning fossil fuels = 7×44/12=~26Gt.
I’ll have to leave it to the more knowledgeable to respond to the effects of aerosols on forcings or temperature. Though,I believe,the numbers on this are still (sorry about this) up in the air.
Mark, the ABC refers to the Asian Brown Cloud which is mainly made up of soot aerosols from polluted air in China and India. Note to the current administration- Don’t propose changing to dung cooking as an alternate fuel. :)
Does anyone have any ideas on the aerosol issue. I thought this would be a central component of the thread, but I have not seen it discussed. Surely to know where we stand right now we need to know how much “current” GW is being masked by daily inputs of these aerosols. Is there know way to come up with even a back-of-the-envelope approximation?
“Surely to know where we stand right now we need to know how much “current” GW is being masked by daily inputs of these aerosols. Is there know way to come up with even a back-of-the-envelope approximation?”
In addition to the site given by t_p_ figure
SPM.2 ,of the Summary for Policy Makers of the 2007 report of the Intergovernmental Panel on Climate Change (IPCC)shows radiative forcings of black carbon on snow,as well as direct and cloud albedo effect of aerosols. http://ipccwg1.ucar.edu/wg1/Report/AR4WG1_Print_SPM.pdf
Thanks again. t_p’s figure seems to indicate that direct and indirect (what might those be, I wonder) effects of aerosols add up to more negative forcing than all the positive forcing of CO2 and methane combined since 1770! Can that be right? Am I missing something.
Laurence, I couldn’t get your link to work.
Thanks again. I am always impressed by the high level of expertise exhibited here.